To the Editor:
Although artemisinins are potent and rapidly acting antimalarial drugs, their widespread use for treating patients with
Plasmodium falciparum
malaria raises the question of emerging ...drug resistance.
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Artemisinin monotherapy should not be used in areas where malaria is endemic; it requires an extended administration period and may lead to treatment failure, most frequently because of problems with compliance. Recent reports of high failure rates associated with artemisinin-based combination therapy, as well as in vitro drug-susceptibility data, suggest the possibility of clinical artemisinin resistance along the Thai–Cambodian border.
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We studied the potential emergence of artemisinin resistance using . . .
Summary Background Dihydroartemisinin-piperaquine has been adopted as first-line artemisinin combination therapy (ACT) for multidrug-resistant Plasmodium falciparum malaria in Cambodia because of few ...remaining alternatives. We aimed to assess the efficacy of standard 3 day dihydroartemisinin-piperaquine treatment of uncomplicated P falciparum malaria, with and without the addition of primaquine, focusing on the factors involved in drug resistance. Methods In this observational cohort study, we assessed 107 adults aged 18–65 years presenting to Anlong Veng District Hospital, Oddar Meanchey Province, Cambodia, with uncomplicated P falciparum or mixed P falciparum / Plasmodium vivax infection of between 1000 and 200 000 parasites per μL of blood, and participating in a randomised clinical trial in which all had received dihydroartemisinin-piperaquine for 3 days, after which they had been randomly allocated to receive either primaquine or no primaquine. The trial was halted early due to poor dihydroartemisinin-piperaquine efficacy, and we assessed day 42 PCR-corrected therapeutic efficacy (proportion of patients with recurrence at 42 days) and evidence of drug resistance from the initial cohort. We did analyses on both the intention to treat (ITT), modified ITT (withdrawals, losses to follow-up, and those with secondary outcomes eg, new non-recrudescent malaria infection were censored on the last day of follow-up), and per-protocol populations of the original trial. The original trial was registered with ClinicalTrials.gov , number NCT01280162. Findings Between Dec 10, 2012, and Feb 18, 2014, we had enrolled 107 patients in the original trial. Enrolment was voluntarily halted on Feb 16, 2014, before reaching planned enrolment (n=150) because of poor efficacy. We had randomly allocated 50 patients to primaquine and 51 patients to no primaquine groups. PCR-adjusted Kaplan-Meier risk of P falciparum 42 day recrudescence was 54% (95% CI 45–63) in the modified ITT analysis population. We found two kelch13 propeller gene mutations associated with artemisinin resistance—a non-synonymous Cys580Tyr substitution in 70 (65%) of 107 participants, an Arg539Thr substitution in 33 (31%), and a wild-type parasite in four (4%). Unlike Arg539Thr, Cys580Tyr was accompanied by two other mutations associated with extended parasite clearance (MAL10:688956 and MAL13:1718319). This combination triple mutation was associated with a 5·4 times greater risk of treatment failure (hazard ratio 5·4 95% CI 2·4–12; p<0·0001) and higher piperaquine 50% inhibitory concentration (triple mutant 34 nM 28–41; non-triple mutant 24 nM 1–27; p=0·003) than other infections had. The drug was well tolerated, with gastrointestinal symptoms being the most common complaints. Interpretation The dramatic decline in efficacy of dihydroartemisinin-piperaquine compared with what was observed in a study at the same location in 2010 was strongly associated with a new triple mutation including the kelch13 Cys580Tyr substitution. 3 days of artemisinin as part of an artemisinin combination therapy regimen might be insufficient. Strict regulation and monitoring of antimalarial use, along with non-pharmacological approaches to malaria resistance containment, must be integral parts of the public health response to rapidly accelerating drug resistance in the region. Funding Armed Forces Health Surveillance Center/Global Emerging Infections Surveillance and Response System, Military Infectious Disease Research Program, National Institute of Allergy and Infectious Diseases, and American Society of Tropical Medicine and Hygiene/Burroughs Wellcome Fund.
The recent emergence of artemisinin-resistant Plasmodium falciparum malaria in western Cambodia could threaten prospects for malaria elimination. Identification of the genetic basis of resistance ...would provide tools for molecular surveillance, aiding efforts to contain resistance. Clinical trials of artesunate efficacy were conducted in Bangladesh, in northwestern Thailand near the Myanmar border, and at two sites in western Cambodia. Parasites collected from trial participants were genotyped at 8,079 single nucleotide polymorphisms (SNPs) using a P. falciparum -specific SNP array. Parasite genotypes were examined for signatures of recent positive selection and association with parasite clearance phenotypes to identify regions of the genome associated with artemisinin resistance. Four SNPs on chromosomes 10 (one), 13 (two), and 14 (one) were significantly associated with delayed parasite clearance. The two SNPs on chromosome 13 are in a region of the genome that appears to be under strong recent positive selection in Cambodia. The SNPs on chromosomes 10 and 13 lie in or near genes involved in postreplication repair, a DNA damage-tolerance pathway. Replication and validation studies are needed to refine the location of loci responsible for artemisinin resistance and to understand the mechanism behind it; however, two SNPs on chromosomes 10 and 13 may be useful markers of delayed parasite clearance in surveillance for artemisinin resistance in Southeast Asia.
Background. Increasing rates of failure of artemisinin-based combination therapy have highlighted the possibility of emerging artemisinin resistance along the Thai-Cambodian border. We used an ...integrated in vivo-in vitro approach to assess the presence of artemisinin resistance in western Cambodia. This article provides additional data from a clinical trial that has been published in The New England Journal of Medicine. Methods. Ninety-four adult patients from Battambang Province, western Cambodia, who presented with uncomplicated falciparum malaria were randomized to receive high-dose artesunate therapy (4 mg/kg/day orally for 7 days) or quinine-tetracycline. Plasma concentrations of dihydroartemisinin, in vitro drug susceptibility, and molecular markers were analyzed. Cases meeting all the following criteria were classified as artemisinin resistant: failure to clear parasites within 7 days of treatment or reemergence of parasites within 28 days of follow-up; adequate plasma concentrations of dihydroartemisinin; prolonged parasite clearance; and increased in vitro drug susceptibility levels for dihydroartemisinin. Results. Two (3.3%) of 60 artesunate-treated patients were classified as artemisinin resistant. Their parasite clearance times were prolonged (133 and 95 h, compared with a median of 52.2 h in patients who were cured). These patients had 50% inhibitory concentrations of dihydroartemisinin that were almost 10 times higher than the reference clone W2. Resistance did not appear to be mediated by the pfmdr1 copy number or selected PfATPase6 polymorphisms previously proposed to confer artemisinin resistance. Conclusion. Artemisinin resistance has emerged along the Thai-Cambodian border. The potentially devastating implications of spreading resistance to a drug that currently has no successor call for further studies of this emerging problem. Clinical trial registration. ClinicalTrials.gov identifier NCT00479206.
The emergence of artemisinin resistance has raised concerns that the most potent antimalarial drug may be under threat. The currently recommended daily dose of artesunate (AS) is 4 mg/kg, and is ...administered for 3 days together with a partner antimalarial drug. This study investigated the impact of different AS doses on clinical and parasitological responses in malaria patients from an area of known artemisinin resistance in western Cambodia.
Adult patients with uncomplicated P. falciparum malaria were randomized into one of three 7-day AS monotherapy regimens: 2, 4 or 6 mg/kg/day (total dose 14, 28 and 42 mg/kg). Clinical, parasitological, pharmacokinetic and in vitro drug sensitivity data was collected over a 7-day inpatient period and during weekly follow-up to 42 days.
143 patients were enrolled (n = 75, 40 and 28 to receive AS 2, 4 and 6 mg/kg/day respectively). Cure rates were high in all treatment groups at 42 days despite almost half the patients remaining parasitemic on Day 3. There was no impact of increasing AS dose on median parasite clearance times, median parasite clearance rates or on the proportion of patients remaining parasitemic on Day 3. However at the lowest dose used (2 mg/kg/d) patients with parasitemia >10,000/µL had longer median (IQR) parasite clearance times than those with parasitemia <10,000/µL (63 (48-75) vs. 84 (66-96) hours, p<0.0001). 19% of patients in the high-dose arm developed neutropenia (absolute neutrophil count <1.0×10(9)/L) by Day 14 and resulted in the arm being halted early.
There is no pharmacodynamic benefit of increasing the daily dose of AS (4 mg/kg) currently recommended for short-course combination treatment of uncomplicated malaria, even in regions with emerging artemisinin resistance, as long as the partner drug retains high efficacy.
ClinicalTrials.gov NCT00722150.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Emerging antimalarial drug resistance in mobile populations remains a significant public health concern. We compared two regimens of dihydroartemisinin-piperaquine in military and civilians on the ...Thai-Cambodian border to evaluate national treatment policy.
Efficacy and safety of two and three-day regimens of dihydroartemisinin-piperaquine were compared as a nested open-label evaluation within a malaria cohort study in 222 otherwise healthy volunteers (18% malaria-infected at baseline). The first 80 volunteers with slide-confirmed Plasmodium falciparum or vivax malaria were randomized 1:1 to receive either regimen (total dose 360 mg dihydroartemisinin and 2880 mg piperaquine) and followed weekly for up to 6 months. The primary endpoint was malaria recurrence by day 42. Volunteers with vivax infection received primaquine at study discharge with six months follow-up.
Eighty patients (60 vivax, 15 falciparum, and 5 mixed) were randomized to dihydroartemisinin-piperaquine. Intention-to-treat all-species efficacy at Day 42 was 85% for the two-day regimen (95% CI 69-94) and 90% for the three-day regimen (95% CI 75-97). PCR-adjusted falciparum efficacy was 75% in both groups with nearly half (45%) still parasitemic at Day 3. Plasma piperaquine levels were comparable to prior published reports, but on the day of recrudescence were below measurable in vitro piperaquine IC50 levels in all falciparum treatment failures.
In the brief period since introduction of dihydroartemisinin-piperaquine, there is early evidence suggesting declining efficacy relative to previous reports. Parasite IC50 levels in excess of plasma piperaquine levels seen only in treatment failures raises concern for clinically significant piperaquine resistance in Cambodia. These findings warrant improved monitoring of clinical outcomes and follow-up, given few available alternative drugs.
ClinicalTrials.gov NCT01280162.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Little is known about circulation of influenza and other respiratory viruses in remote populations along the Thai-Cambodia border in western Cambodia. We screened 586 outpatients (median age 5, range ...1-77) presenting with influenza-like-illness (ILI) at 4 sentinel sites in western Cambodia between May 2010 and December 2012. Real-time reverse transcriptase (rRT) PCR for influenza was performed on combined nasal and throat specimens followed by viral culture, antigenic analysis, antiviral susceptibility testing and full genome sequencing for phylogenetic analysis. ILI-specimens negative for influenza were cultured, followed by rRT-PCR for enterovirus and rhinovirus (EV/RV) and EV71. Influenza was found in 168 cases (29%) and occurred almost exclusively in the rainy season from June to November. Isolated influenza strains had close antigenic and phylogenetic relationships, matching vaccine and circulating strains found elsewhere in Cambodia. Influenza vaccination coverage was low (<20%). Western Cambodian H1N1(2009) isolate genomes were more closely related to 10 earlier Cambodia isolates (94.4% genome conservation) than to 13 Thai isolates (75.9% genome conservation), despite sharing the majority of the amino acid changes with the Thai references. Most genes showed signatures of purifying selection. Viral culture detected only adenovirus (5.7%) and parainfluenza virus (3.8%), while non-polio enteroviruses (10.3%) were detected among 164 culture-negative samples including coxsackievirus A4, A6, A8, A9, A12, B3, B4 and echovirus E6 and E9 using nested RT-PCR methods. A single specimen of EV71 was found. Despite proximity to Thailand, influenza epidemiology of these western Cambodian isolates followed patterns observed elsewhere in Cambodia, continuing to support current vaccine and treatment recommendations from the Cambodian National Influenza Center. Amino acid mutations at non-epitope sites, particularly hemagglutinin genes, require further investigation in light of an increasingly important role of permissive mutations in influenza virus evolution. Further research about the burden of adenovirus and non-polio enteroviruses as etiologic agents in acute respiratory infections in Cambodia is also needed.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Mixed P. falciparum/P. vivax infections are common in southeast Asia. When patients with P. falciparum malaria are treated and followed for several weeks, a significant proportion will develop P. ...vivax malaria. In a combined analysis of 243 patients recruited to two malaria treatment trials in western Cambodia, 20/43 (47%) of those with P. falciparum gametocytes on admission developed P. vivax malaria by Day 28 of follow-up. The presence of Pf gametocytes on an initial blood smear was associated with a 3.5-fold greater rate of vivax parasitemia post-treatment (IRR = 3.5, 95% CI 2.0-6.0, p<0.001). The increased rate of post-treatment P. vivax infection persisted when correlates of exposure and immunity such as a history of malaria, male gender, and age were controlled for (IRR = 3.0, 95% CI 1.9-4.7, p<0.001). Polymerase chain reaction (PCR) confirmed that only a low proportion of subjects (5/55 or 9.1%) who developed vivax during follow-up had detectable Pv parasites in the peripheral blood at baseline. Molecular detection of falciparum gametocytes by reverse transcriptase PCR in a subset of patients strengthened the observed association, while PCR detection of Pv parasitemia at follow-up was similar to microscopy results. These findings suggest that the majority of vivax infections arising after treatment of falciparum malaria originate from relapsing liver-stage parasites. In settings such as western Cambodia, the presence of both sexual and asexual forms of P. falciparum on blood smear at presentation with acute falciparum malaria serves as a marker for possible occult P. vivax coinfection and subsequent relapse. These patients may benefit from empiric treatment with an 8-aminoquinolone such as primaquine.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In vitro drug susceptibility assay of Plasmodium falciparum field isolates processed "immediate ex vivo" (IEV), without culture adaption, and tested using histidine-rich protein-2 (HRP-2) detection ...as an assay, is an expedient way to track drug resistance.
From 2005 to 2010, a HRP-2 in vitro assay assessed 451 P. falciparum field isolates obtained from subjects with malaria in western and northern Cambodia, and eastern Thailand, processed IEV, for 50% inhibitory concentrations (IC50) against seven anti-malarial drugs, including artesunate (AS), dihydroartemisinin (DHA), and piperaquine.
In western Cambodia, from 2006 to 2010, geometric mean (GM) IC50 values for chloroquine, mefloquine, quinine, AS, DHA, and lumefantrine increased. In northern Cambodia, from 2009-2010, GM IC50 values for most drugs approximated the highest western Cambodia GM IC50 values in 2009 or 2010.
Western Cambodia is associated with sustained reductions in anti-malarial drug susceptibility, including the artemisinins, with possible emergence, or spread, to northern Cambodia. This potential public health crisis supports continued in vitro drug IC50 monitoring of P. falciparum isolates at key locations in the region.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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